For the buss at least, I used the UAD SSL 4k Buss Comp for a long time, but using a real buss compressor did make a positive difference. I only paid $1200 for my buss compressor and it has Lundahl output transformers that I can switch back and forth between them and electronically balanced output, so I have a sonic option there as well. But anyway, yes, the real deal made a pretty big difference, especially coming from a console like I now do.

In regards to a real 1176 or La2a. The real deal is nicer, but UA did come scary close with their models of their own units. However, for me, on mixdown, I basically use 14 channels on my board to sum down to. My board has 8 busses and that's where I'm using real compressors. However, I'm not even using fancy compressors here. I basically use a 1066 for busses 1/2 which is all drums. I use an FMR RNLA for guitars/bass on 3/4, then an FMR RNC for vocals on 5/6 and lastly, all my effects, delays, verbs go to busses 7/8, but I'm not doing anything there as I've EQ'd compressed them itb. My only compressor that ran me over $1k is my buss compressor and it's all I feel I need to make mixes sound good. Yes, I want more, but I don't need them. I did it for years all itb and before I had my board and anything to use outboard.